RFR: 8301822: BasicLookAndFeel does not need to check for null after checking for type

[Sergey Bylokhov]

On Mon, 16 Jan 2023 20:30:08 GMT, SWinxy <duke at openjdk.org> wrote:

> BasicLookAndFeel checks an instanceof in its `AWTEventHelper` listener class, but the result of that will always be non-null. The check should be removed.

Marked as reviewed by serb (Reviewer).

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PR: https://git.openjdk.org/jdk/pull/12019